Bottom-up Arbitrary-shape Scene Text Detectors: These detectors can be divided into pixel-wise based methods and component-wise based methods. The former ones [1]}, [2]}, [3]}, [4]}, [5]}, [6]}, [7]}, [8]}, [9]}, [10]} predict the auxiliary information of each pixel or the specific pixel in the entire/shrunk text region to better formulate different text instances. For example, PSENet [1]} introduces a progressive scale expansion algorithm to fuse multi-shrunk segmentation maps with the help of text region kernels. Similarly, PAN [4]} estimates the embedding vectors of pixels to measure the distances to different text kernels. Besides, MSR [3]} and TextField [9]} learn the offset field of each pixel in text regions for better linking neighbor pixels. Furthermore, TextRay [8]} predicts the text center heatmap and multiple rays rooted at the specific text center pixels, which can directly reconstruct the text instances and thus avoid the clustering process.
